Planning For 'Curiosity' On Mars

If all goes according to plan, the Mars Science Laboratory rover, nicknamed 'Curiosity,' will touch down on the red planet this weekend following what NASA has called 'seven minutes of terror' during the descent. NPR science correspondent Joe Palca and John Grunsfeld, head of NASA's Science Directorate, give a preview of the mission and talk about what scientists hope to learn from the latest ambassador to Mars.